The immunohistochemical identification of antigens on tissue sections has become an integral and valuable part of modern histopathology. Antigens are localized either by immunofluorescent techniques or by enzyme- substrate methods on embedded or frozen materials. Although these methods are routine for soft tissue samples, immunohistochemical examination of osteocartilaginous tissues is made difficult by the material properties of bone and cartilage. Special techniques are required to process nondecalcified bone for immunohistochemistry such as the use of water soluble, cold polymerizing plastics or the use of special adhesives, supports, and slides after thin sectioning of frozen material on a motorized cryostat. With these techniques one can identify antigens present on the surface of cells, whether in inflammatory infiltrates, in cartilage, bone, synovium, or any other tissue; and noncellular antigens present within the matrix. The objective of the Immunohistochemistry Core of the northeast ohio multipurpose Arthritis Center is to continue to function as a shared resource and centralized facility for the production of monoclonal antibodies relevant to musculoskeletal research and for the processing, embedding, cutting, and immunohistochemical staining of bone, cartilage, and joint-related samples generated as part of on-going research activities of center personnel. The centralization of the immunohistochemistry laboratory provides economy of supplies, equipment, and effort; offers new technology to investigators not currently using these techniques; and promotes interactions among the various investigators in the NEOMAC.